//: C08:Mutable.cpp
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// The "mutable" keyword

class Z
{
    int i;
    mutable int j;
public:
    Z();
    void f() const;
};

Z::Z()
{
    i = j = 0;
}

void Z::f() const
{
//! i++; // Error -- const member function
    j++; // OK: mutable
}

int main()
{
    const Z zz;
    zz.f(); // Actually changes it!
} ///:~
